Refactor snapshot-merge deptree and device removal to support info-by-uuid

Add a merging snapshot to the deptree, using the "error" target, rather
than avoid adding it entirely.  This allows proper cleanup of the -cow
device without having to rename the -cow to use the origin's name as a
prefix.

Move the preloading of the origin LV, after a merge, from
lv_remove_single() to vg_remove_snapshot().  Having vg_remove_snapshot()
preload the origin allows the -cow device to be released so that it can
be removed via deactivate_lv().  lv_remove_single()'s deactivate_lv()
reliably removes the -cow device because the associated snapshot LV,
that is to be removed when a snapshot-merge completes, is always added
to the deptree (and kernel -- via "error" target).

Now when the snapshot LV is removed both the -cow and -real devices
get removed using uuid rather than device name.  This paves the way
for us to switch over to info-by-uuid queries.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 32 insertions, 5 deletions

diff --git a/lib/metadata/snapshot_manip.c b/lib/metadata/snapshot_manip.c
index 19effe38..f7218c26 100644
--- a/lib/metadata/snapshot_manip.c
+++ b/lib/metadata/snapshot_manip.c
@@ -15,6 +15,7 @@
 
 #include "lib.h"
 #include "metadata.h"
+#include "locking.h"
 #include "toolcontext.h"
 #include "lv_alloc.h"
 
@@ -58,9 +59,9 @@ int lv_is_merging_origin(const struct logical_volume *origin)
 
 struct lv_segment *find_merging_cow(const struct logical_volume *origin)
 {
-	/* FIXME: eliminate this wrapper and just use find_cow()?
-	 * - find_merging_cow() adds to code clarity in caller
-	 */
+	if (!lv_is_merging_origin(origin))
+		return NULL;
+
 	return find_cow(origin);
 }
 
@@ -170,12 +171,22 @@ int vg_add_snapshot(struct logical_volume *origin,
 
 int vg_remove_snapshot(struct logical_volume *cow)
 {
+	int preload_origin = 0;
 	struct logical_volume *origin = origin_from_cow(cow);
 
 	dm_list_del(&cow->snapshot->origin_list);
 	origin->origin_count--;
-	if (find_merging_cow(origin) == find_cow(cow))
-		clear_snapshot_merge(origin_from_cow(cow));
+	if (find_merging_cow(origin) == find_cow(cow)) {
+		clear_snapshot_merge(origin);
+		/*
+		 * preload origin to:
+		 * - allow proper release of -cow
+		 * - avoid allocations with other devices suspended
+		 *   when transitioning from "snapshot-merge" to
+		 *   "snapshot-origin after a merge completes.
+		 */
+		preload_origin = 1;
+	}
 
 	if (!lv_remove(cow->snapshot->lv)) {
 		log_error("Failed to remove internal snapshot LV %s",
@@ -186,5 +197,21 @@ int vg_remove_snapshot(struct logical_volume *cow)
 	cow->snapshot = NULL;
 	lv_set_visible(cow);
 
+	if (preload_origin) {
+		if (!vg_write(origin->vg))
+			return_0;
+		if (!suspend_lv(origin->vg->cmd, origin)) {
+			log_error("Failed to refresh %s without snapshot.",
+				  origin->name);
+			return 0;
+		}
+		if (!vg_commit(origin->vg))
+			return_0;
+		if (!resume_lv(origin->vg->cmd, origin)) {
+			log_error("Failed to resume %s.", origin->name);
+			return 0;
+		}
+	}
+
 	return 1;
 }